brazing beginner

I'm making a CNC machine and I need to make a frame and I decided to use aluminum since it's surprisingly the cheapest. I need to braze the joints to gather and I'm new to brazing. Is all I need: Propane bottle Nozzle someway to ignite it brass solder If anyone here is an experience brazer than please give me some tips

sort by: active | newest | oldest
Rishnai9 years ago
Aluminum is highly reactive. There's a reason that you don't just arc or torch weld aluminum: if it "works" it will be ugly and brittle. Most of the time you'll just ruin things and make a mess. You'll need to do what's called "heliarc" or TIG welding. It shrouds the electrode and hot bead with an inert gas, and is rather touchy if you're just learning. Despite the name, helium is no longer the favored gas: it floats up, rather than sinking onto the work. You'd need to use argon. If you weren't making something that needs to have precise distances like a CNC machine, I'd suggest "poor man's TIG," which is arc welding with aluminum rod, but the sheild gas is being dumped on by your oxy torch hooked up to the Ar bottle. Since you are making a CNC machine, I say use iron, mechanically fasten things, or have a certified welder do it properly.
turn-n-burn9 years ago
I know Im several days late and a buck or two short, but AC high frequency TIG is your best. The concept for the orpeator/welder is basically the same as oxy/accet., flame welding, except that your TIG torch does not have the same kind or flame, infact its not a flame at all its sort of a controlled electrical arc. Thats describing it the best I can. If your're in a shop, you could find out exactly what Im talking about. Peace!
guyfrom7up (author) 10 years ago
ok thanks! So i should try to aim for an iron like metal. If alluminum melts at a low temperature, than couldn't I kind of just weld it?
If you're set on AL, you're gonna need to either mechanically fasten it, or WELD it.

Emphasis mine ;-) AL repair rod

My advise is to practice welding before attempting this, though.
guyfrom7up (author)  Goodhart10 years ago
what does AL stand for, aluminum? The surfaces to be joined?
al = aluminum, yes ....sorry. I just copied what was said before.
ironsmiter10 years ago
wow. just wow. aluminium is NOT the thing to learn brazing on! period!
aluminium MELTS at 1220F
Brazing brass rod flows around 1652F
And that's not even counting the extremely high heat dispersion rate of AL.

If you're set on AL, you're gonna need to either mechanically fasten it, or WELD it.

Simple Answer: yes
AL repair rod
source of heat(shoot for at least 800F METAL tempature. propane with a turbo nozzel should work fine)
striker/match/campfire
SAFETY GEAR(glasses, gloves, longsleeve cotton shirt, jeans, boots)
and you should be all set to begin learning.

http://durafix.com/ makes a "Brazing" repair rod for use with propane torches.
(just the first one google turned up) a few other companies too. basically, the rod creates an alloy at the bonding surface with a lower-than AL melting tempature... then the molten filler rod solidifies. this creates a "looks like aluminium" material, welded into the main part. Tig and Mig welding are options, but even experienced welders can have trouble with this material. Burnthrough and tangled mig wire are both fairly common, when first learning.

Brass brazing rod is mainly for use on iron based material(steel, cast iron, ductile iron, etc.).